1. Field of the Invention
The present invention relates to marine cargo barges generally and, more particularly, but not by way of limitation, to a novel integrated tug/barge system having a riding pusher boat to propel the integrated tug/barge.
2. Background Art
There are two "Integrated Tug/Barge" (ITB) modes provided by United States Coast Guard (USCG) Regulations: (1) towing a barge with a tug boat, and (2) a dual purpose mode which consists of towing and pushing. Pushing is relatively superior to towing in maneuvering a barge because of the greater degree of control a tug boat has over a barge when pushing it. There are two operation methods when pushing a barge: (1) a tug boat is used to push the barge's stern, such as in Mississippi River barge operations, with the tug and barge tied together by lines, and (2) a tug boat located in a notch in the stern of the barge propels the barge, with the tug boat and barge being joined by lines or by pivoting arms. A variation of the first pushing method is to have the tug boat lashed alongside the barge. These methods work well in calm seas.
In rough seas, a large differential in motion between the tug boat and the barge, especially pitching motion, can occur, due to different wave heights and directions for the tug and the barge because the tug boat and barge have different buoyancies which results in unequal wave height. While the barge might pass through certain waves with little or no pitching motion, the tug boat might experience a very heavy pitching motion and one at a different frequency than that experienced by the barge, due to the foregoing reasons. Therefore, collision damage to the barge notch can occur, due to the rough motion of the bow of the tug boat. Also, joint arm damage can occur, due to severe torque resulting from unbalanced wave motion.
There have been documented several major damage incidents in barge transportation the main causes of which were the poor and unstable conditions in ITBs. Many articles have been written stating that further improvement of ITB systems is required for the safe working of barges in United States waters.
Accordingly, it is a principal object of the present invention to provide a system to join a tug boat and a barge in such a manner as to avoid the differential motion problems described above.
It is a further object of the invention to provide such a system that provides for rapid unjoining of the tug boat in the event of an emergency.
It is an additional object of the invention to provide such a system which can be easily employed.
It is another object of the invention to provide such a system in which the tug boat can mount the barge under its own power.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will be elucidated in, or be apparent from, the following description and the accompanying drawing figures.